Font Management in Linux, Part 1 - page 2
The three main font formats are TrueType, OpenType, and PostScript. TrueType fonts have a
.ttf extension on Linux/Unix, Windows, and Mac OS X, plus
.ttc on the Mac. TrueType fonts scale up and down in size gracefully without jagged edges or inconsistencies in line thickness; you don't need a separate file for each size, but only for different styles like italic or bold.
PostScript fonts need two files each:
.afm is the screen font, and
.pfb is the printer font. This is specific to Linux and Unix; Windows PostScript fonts are
.pfb. Mac OS X handles PostScript fonts in a number of different ways that I don't even want to get entangled in, involving suitcases and forks and other oddments.
OpenType is a newer font format developed jointly by Microsoft and Adobe, their "can't we all just get along" format. Its file extension is
.otf, and it works on both Windows and Mac.
Bitmap fonts are an old format. You need a separate font file for each size and style, so as you can imagine hardly anyone uses them anymore.
Most Linuxes these days come with both TrueType and PostScript Type 1 fonts. Finicky desktop publishers insist on using PostScript fonts with genuine PostScript printers, but these are becoming rare. Most printers support some form of PostScript emulation. Ghostscript is a PostScript interpreter that comes standard on most Linux distributions, so you should always be able to read and print PostScript documents.